The present invention relates to an apparatus and method for predicting a braking distance of a vehicle. The braking distance of a vehicle refers to a distance at which a vehicle having a plurality of wheels travels during a period from a commencement of a braking operation for stopping the vehicle to a complete stop of the vehicle, in the case where the braking operation is started while the vehicle is traveling.
In these days, a number of automobile vehicles have an antilock-brake system (ABS) so as to travel more safety. The ABS is operated in the case where an attempt is made so as to stop a traveling automobile vehicle suddenly, and prevents wheels from being locked during a braking operation, thereby minimizing the distance (braking distance) at which the vehicle travels during a period from the commencement of the braking operation of the vehicle to the complete stop of the vehicle.
However, as a matter of course, although the ABS has an effect of relatively decreasing a braking distance, it does not completely eliminate the braking distance itself. In order to allow an automobile vehicle to travel safely, a driver driving the vehicle needs to know as exactly as possible to which degree the vehicle travels before stopping, i.e., the length of a braking distance required for the vehicle to stop, in the case of attempting to stop the traveling vehicle. If the driver during driving exactly knows such a braking distance, for example, a driver driving a vehicle can exactly keep a distance required for safety between the vehicle driven by the driver and a vehicle traveling ahead of the vehicle driven by the driver. Further, for example, in the case of finding an obstacle ahead of the traveling vehicle, the driver can perform a braking operation at a suitable timing to stop the vehicle safely. In order to allow the vehicle to travel safely, it is necessary that the driver driving the vehicle knows the braking distance of the vehicle during driving of the vehicle.
Generally, as a rough index of the braking distance of a vehicle, an index in accordance with the vehicle speed during traveling and the like are known. However, the actual braking distance of a vehicle is associated with various factors such as the state of tires and the condition of a road surface, and hence, the braking distance of a vehicle varies largely depending upon the state of tires and the condition of a road surface. Therefore, a driver driving a vehicle cannot exactly know the braking distance of the vehicle during driving of the vehicle. JP 2003-182476 A discloses a road surface condition and tire traveling state estimating apparatus for estimating the traveling state of tires during traveling and the condition (road surface friction coefficient etc.) of a road surface with which the tires are in contact.